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Subject[PATCH 5.10 098/167] sctp: update active_key for asoc when old key is being replaced
From: Xin Long <>

[ Upstream commit 58acd10092268831e49de279446c314727101292 ]

syzbot reported a call trace:

BUG: KASAN: use-after-free in sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
Call Trace:
sctp_auth_shkey_hold+0x22/0xa0 net/sctp/auth.c:112
sctp_set_owner_w net/sctp/socket.c:131 [inline]
sctp_sendmsg_to_asoc+0x152e/0x2180 net/sctp/socket.c:1865
sctp_sendmsg+0x103b/0x1d30 net/sctp/socket.c:2027
inet_sendmsg+0x99/0xe0 net/ipv4/af_inet.c:821
sock_sendmsg_nosec net/socket.c:703 [inline]
sock_sendmsg+0xcf/0x120 net/socket.c:723

This is an use-after-free issue caused by not updating asoc->shkey after
it was replaced in the key list asoc->endpoint_shared_keys, and the old
key was freed.

This patch is to fix by also updating active_key for asoc when old key is
being replaced with a new one. Note that this issue doesn't exist in
sctp_auth_del_key_id(), as it's not allowed to delete the active_key
from the asoc.

Fixes: 1b1e0bc99474 ("sctp: add refcnt support for sh_key")
Signed-off-by: Xin Long <>
Signed-off-by: David S. Miller <>
Signed-off-by: Sasha Levin <>
net/sctp/auth.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/sctp/auth.c b/net/sctp/auth.c
index 6f8319b828b0..fe74c5f95630 100644
--- a/net/sctp/auth.c
+++ b/net/sctp/auth.c
@@ -860,6 +860,8 @@ int sctp_auth_set_key(struct sctp_endpoint *ep,
if (replace) {
+ if (asoc && asoc->active_key_id == auth_key->sca_keynumber)
+ sctp_auth_asoc_init_active_key(asoc, GFP_KERNEL);
list_add(&cur_key->key_list, sh_keys);


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